An image reading device illuminates an object having an uneven surface with light having a great depth of illumination to clearly scan the object.
Patent Literature 1 describes an image reading device in which light is emitted from a light source array with an optical axis of the light source array extending toward a manuscript, light emitted from the light source is made to enter a light guide and then is reflected on the reflective surface of the light guide toward the manuscript so that the manuscript is illuminated. Patent Literature 1 describes that the reflective surface includes multiple continuous flat surfaces.
Patent Literature 2 describes an illumination device in which one end of a flat surface as a light beam incident surface crosses one end of a flat surface as a light beam emission surface at substantially right angles and the other end of the flat surface as a light beam incident surface is connected to the other end of the flat surface as a light beam incident surface by an elliptic curve serving as a concave reflector.
Patent Literature 3 describes an illumination unit in which light-emitting diode (LED) chips emit light toward a cylindrical parabolic mirror, and the light enters a cylindrical parabolic block through the incident surface of the cylindrical parabolic block. The light is internally reflected by the cylindrical parabolic mirror, and the reflected light is emitted as a substantially collimated light beam, from the prismatic emission surface of the cylindrical parabolic block onto an area to be illuminated.